Paul Bolton is a Guest Professor in the Department of Medical Physics at the Ludwig-Maximilians-Universität München in München, Germany. Katia Parodi is a Professor and Chair of Medical Physics in the Department of Medical Physics at the Ludwig-Maximilians-Universität München in München, Germany. Jörg Schreiber is an Associate Professor in the Department of Medical Physics at the Ludwig-Maximilians-Universität München in München, Germany.